Abstract

2349

We have previously shown that primary brain tumors which express a high MW protein undergo apoptosis upon exposure to vitamin D (Biochem. Pharm 60:1361,2000). By screening a cDNA library obtained from a cell line (Glioma 1) which highly express this protein, we have identified the gene which encodes this protein to be procollagen alpha 1 type 1. We have examined 41 primary brain tumors and 2 metastatic lung cancers to the brain. Our results showed that 14/15 intermediate and low grade glioma express procollagen type including 12 which express high levels. In contrast, only 12/21 high grade glioma express procollagen type1 and only 4/12 express high levels. Thus, our data suggest that procollagen alpha 1 type I is more commonly found in low and intermediate grade glioma. Interestingly, primary culture derived from tumors expressing procollagen type 1 are more sensitive to the growth inhibitory effect of VD3 (6-36 nM) while tumors which lack procollagen type have ID50> 100 nM. Gene specific array analysis in cell lines which express procollagen alpha 1 type 1 demonstrated that tumor cells which possess procollagen type 1 possess fibronectin, PTEN, p-53 while tumor cells lacking procollagen type 1 do not express these gene. Instead, they have higher levels of AKT 1, AKT 2 and P70S6 kinase. We have obtained a full length cDNA of procollagen alpha type 1 and transfected into U-373 cells which lack procollagen alpha 1 type 1 expression. These transfectants are more sensitive to VD3 with the ID50 decreasing from 80 to 40 nM. They also expressed fibronectin. Morphologically, these transfectants resemble cell lines which express procollagen alpha I type I. These transfectants (clone M2, M4) also express higher levels of integrin alpha 1/beta1 but lower levels of integrin beta 8 which is similar to those cell lines which express procollagen alpha 1 type 1. The signaling pathways which involve procollagen type 1 in cellular differentiation/ proliferation and their relationship with vitamin D sensitivity are currently under investigation.